Emi Nakato

Distinct differences in the pattern of hemodynamic response to happy and angry facial expressions in infants--a near-infrared spectroscopic study.

Recognition of other peoples facial expressions of emotion plays an important role in social communication in infants as well as adults. Evidence from behavioral studies has demonstrated that the ability to recognize facial expressions develops by 6 to 7 months of age. Although the regions of the infant brain involved in processing facial expressions have not been investigated, neuroimaging studies in adults have revealed that several areas including the superior temporal sulcus (STS) participate in the processing of facial expressions. To examine whether the temporal area overlying the STS is responsible for the processing of facial expressions in infants, near-infrared spectroscopy (NIRS) was used to measure the neural activity in the temporal area overlying the STS as infants looked at happy and angry faces. NIRS provides a non-invasive means of estimating cerebral blood flow in the human brain and does not require severe constraints of head-movement. According to the International 10-20 system for EEG electrode placement, the measurement area was located in the bilateral temporal area centered at positions T5 and T6, which correspond to the STS. The time-course of the average change in total-Hb concentration revealed a clear difference in the pattern of hemodynamic responses to happy and angry faces. The hemodynamic response increased gradually when infants looked at happy faces and was activated continuously even after the disappearance of the face. In contrast, the hemodynamic responses for angry faces increased during the presentation of angry faces, then decreased rapidly after the face disappeared. Moreover, the left temporal area was significantly activated relative to the baseline when infants looked at happy faces, while the right temporal area was significantly activated for angry faces. These findings suggest hemispheric differences in temporal areas during the processing of positive and negative facial expressions in infants.

Do Infants Represent the Face in a Viewpoint-Invariant Manner? Neural Adaptation Study as Measured by Near-Infrared Spectroscopy

Recent adult functional magnetic resonance imaging (fMRI) studies reported that face-sensitive cortical areas showed attenuated responses to the repeated presentation of an identical facial image compared to the presentation of different facial images (fMRI-adaptation effects: e.g., Andrews and Ewbank, 2004). Building upon this finding, the current study, employing the adaptation paradigm, used near-infrared spectroscopy (NIRS) to explore the neural basis of face processing in infants. In Experiment 1, we compared hemodynamic responses in the bilateral temporal regions during the repeated presentation of the same face (the same-face condition) and the sequential presentation of different faces (the different-face condition). We found that (1) hemodynamic responses in the channels around the T5 and T6 regions increased during the presentation of different faces compared to those during the presentation of different objects; and that (2) these channels showed significantly lower response in the same-face condition than in the different-face condition, demonstrating the neural adaptation effect in 5- to 8-month-olds as measured by NIRS. In Experiment 2, when faces in both the same-face and different-face conditions were changed in viewpoint, lower hemodynamic responses in the same-face condition were found in 7- to 8-month-olds but not in 5- to 6-month-olds. Our results suggest that faces are represented in a viewpoint-invariant manner in 7- and 8-month-old infants.

Do infants recognize the Arcimboldo images as faces? Behavioral and near-infrared spectroscopic study.

Arcimboldo images induce the perception of faces when shown upright despite the fact that only nonfacial objects such as vegetables and fruits are painted. In the current study, we examined whether infants recognize a face in the Arcimboldo images by using the preferential looking technique and near-infrared spectroscopy (NIRS). In the first experiment, we measured looking preference between upright and inverted Arcimboldo images among 5- and 6-month-olds and 7- and 8-month-olds. We hypothesized that if infants perceive the Arcimboldo images as faces, they would prefer the upright images to the inverted ones. We found that only 7- and 8-month-olds significantly preferred upright images, suggesting that they could perceive the Arcimboldo images as faces. In the second experiment, we measured hemodynamic responses using NIRS. Based on the behavioral data, we hypothesized that 7- and 8-month-olds would show different neural activity for upright and inverted Arcimboldo images, as do adults. Therefore, we measured hemodynamic responses in 7- and 8-month-olds while they were looking at upright and inverted Arcimboldo images. Their responses were then compared with the baseline activation during the presentation of individual vegetables. We found that the concentration of oxyhemoglobin increased in the left temporal area during the presentation of the upright images compared with the baseline during the presentation of vegetables. The results of the two experiments suggest that (a) the ability to recognize the upright Arcimboldo images as faces develops at around 7 or 8 months of age and (b) processing of the upright Arcimboldo images is related to the left temporal area of the brain.

Hemodynamic response of children with attention-deficit and hyperactive disorder (ADHD) to emotional facial expressions

Children with attention-deficit/hyperactivity disorder (ADHD) have difficulty recognizing facial expressions. They identify angry expressions less accurately than typically developing (TD) children, yet little is known about their atypical neural basis for the recognition of facial expressions. Here, we used near-infrared spectroscopy (NIRS) to examine the distinctive cerebral hemodynamics of ADHD and TD children while they viewed happy and angry expressions. We measured the hemodynamic responses of 13 ADHD boys and 13 TD boys to happy and angry expressions at their bilateral temporal areas, which are sensitive to face processing. The ADHD children showed an increased concentration of oxy-Hb for happy faces but not for angry faces, while TD children showed increased oxy-Hb for both faces. Moreover, the individual peak latency of hemodynamic response in the right temporal area showed significantly greater variance in the ADHD group than in the TD group. Such atypical brain activity observed in ADHD boys may relate to their preserved ability to recognize a happy expression and their difficulty recognizing an angry expression. We firstly demonstrated that NIRS can be used to detect atypical hemodynamic response to facial expressions in ADHD children.

19. A near-infrared spectroscopic study on the mother’s face perception in infants

direct pathways. We tried to establish a procedure to quantify functions of PNs. Surface electromyogram was recorded from the right or left biceps muscle (Bi) of normal human subjects (n = 13). During weak tonic voluntary contraction of Bi and hand muscles, (1) electric stimulation of the ipsilateral ulnar nerve, (2) transcranial magnetic stimulation (TMS) of the contralateral primary motor cortex, and (3) combined stimulation of both were delivered. Interstimulus intervals for the combined stimulation were set to ensure simultaneous excitatory inputs on PNs, caused by both stimulations. When appropriate stimulus strength was selected, TMS-induced potentials in Bi were facilitated by combined ulnar stimulation. However, the maximum facilitation was observed on the dominant side in righthanded subjects (n = 10). The tendency was not noted in left-handed subjects (n = 3). Thus, the current procedure is useful to evaluate functions of PNs, though stimulus condition and handedness have to be considered. The asymmetry for the right-handed subjects may be explained by differential pyramidal inputs to PNs, because bilateral reflex effects by ulnar stimulation were similarly weak.

The hollow face illusion in infancy

Abstract presented at The 30th European Conference on Visual Perception, 27-31 August 2007, Arezzo, Italy